Vintage Asylum

Fisher 500 T

71.166.90.246

I bought a Fisher 500T, and a service manual for it online. It's in great cosmetic condition. I fired the unit up, and it works! Sort of. The FM tuner is really first rate, pulling in a fairly distant station very well with a mere dipole antenna. All the FM indicators and dial lamps work. Unfortunately, the right channel is much weaker than the left, and it seems to sound thin, regardless of the lower volume.
Before trying any surgery, I'd first like to set idling current (i.e., bias) and "power amplifier center voltage", as the manual calls it. But for this purpose, the service manual I obtained is fairly useless. For example, it refers to pots for setting idling current that don't appear on a schematic or board layout. The manual is for SN's beginning 20001, and mine is SN 33490. The manual must be missing a page or two. What's frustrating is that I can see what are obviously two trimpots on each of two power amp driver boards, one for bias, the other for center voltage, but I don't know which is which, or where to connect test leads.
Does anyone have a complete service manual, or at least the layouts/schematics of the appropriate boards on which these adjustments can be made?
My 500-T started life as a 220V unit, then was converted to 115V. On the back is a little plate stating "Egli, Fischer, & Co., AG, Zurich"
Also, any conjectures on the problem with the channel imbalance I mentioned? I think it may be in the preamp section, in the tone controls, and several capacitors need to be replaced. But that's only a very imprecise hunch.
EDIT: I forgot to mention that I tried applying deoxIT to the controls (volume, balance, etc.) as well as I could - most of the controls in the 500T are closed and it's virtually impossible to get deoxIT in. In most cases like mine, a deoxIT treatment helps, but not in this one.

Edits: 06/26/07

Follow Ups:

RE: Fisher 500 T - ako_hobby 14:03:38 06/26/07 (0)
RE: Fisher 500 T - Brian Levy 12:15:42 06/26/07 (0)

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